JPH11323009A - Recycling of polyurethane foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for recycling a polyurethane foam by adding an azole compound to the crushed product of the polyurethane foam and subsequently thermally decomposing the polyurethane foam to produce a polyol component as a decomposition product, capable of recovering the polyol component useful as a reaction component for producing the polyurethane foam as the decomposition treatment product. SOLUTION: This method for recycling a polyurethane foam comprises adding an azole compound (preferably a triazole compound such as 3-amino-1,2,4-triazole or benzotriazole) as a decomposing agent to the crushed polyurethane foam (preferably having a particle diameter of 5-15 mm) and subsequently thermally decomposing the polyurethane foam to produce a polyol component as a decomposition product. The azole compound is preferably used in an amount of 0.1-1.0 wt.%, and the thermal decomposition treatment is carried out, for example, in a reactor with a heating oven, an autoclave reactor, a heating kneader type reactor, an extrusion type reactor, etc., generally at 180-200 deg.C for 5-20 min.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyurethane foam recycling method for decomposing a waste polyurethane foam to obtain a polyol component useful as a reaction component for producing a polyurethane foam.

[0002]

2. Description of the Related Art The use of polyurethane foam has expanded,
Its effective reuse is becoming increasingly important.
In the case of automobiles, flexible, semi-rigid and rigid polyurethane foams are often used for seat cushions, headrests / armrests, heat insulators for refrigerators and the like. On the other hand, when an automobile is scrapped, such a polyurethane foam cannot be easily recycled because it is (1) bulky because of a low-density foam, and (2) it is a thermosetting resin. For this reason, at present, they are shredded and landfilled or incinerated. Several methods have heretofore been proposed for such polyurethane foam recycling methods. The main part will be described below.

As a method of recycling a polyurethane foam, a material recycling method, a chemical recycling method, and a thermal recycling method have been conventionally studied.

In the above-mentioned material recycling law,
An adhesive pressing method in which polyurethane foam pulverized and chipped products are pressed and bonded using an adhesive, a polyurethane foam pulverization method and a filler method in which the polyurethane foam is used as a filler, or a polyurethane foam pulverized and heated at a high temperature. Heat compression molding methods of molding at high pressure have been tried, but in any case, densification is unavoidable and cannot be recycled as a low-density foam. That is, in the case of the adhesive press method,
Addition of the adhesive and compression molding in the pressing process result in a high-density foam, and in the case of the filler method, a special pulverizer with a cooling function is required for fine pulverization, otherwise polyurethane foam is generated due to heat generated during pulverization. When the obtained finely pulverized material is added as a filler, the physical properties of the foam are deteriorated and the desired low-density polyurethane foam cannot be obtained. In the case of the heat compression molding method, a molded product obtained from the molding mechanism becomes a non-foamed body. In the case of the above method, particularly in the case of the heat compression molding method, it is shown that the polyurethane foam classified as a thermosetting resin undergoes compression molding when heated, but this causes dissociation or decomposition of urethane bonds during heating. It is explained that it is.

In the above-mentioned chemical recycling method, a method of chemically decomposing a polymer chain forming a polyurethane foam has been attempted. For example, JP-A-7-2
No. 24141 discloses a method in which flexible polyurethane foam waste is heated to 160-180 ° C. in the presence of a polyhydric alcohol, an alkali metal hydroxide and water to perform a decomposition liquefaction treatment, and the resulting decomposition product is dehydrated under reduced pressure. After drying, propylene oxide is added in an autoclave to obtain a regenerated polyol. That is, the decomposed product obtained first in the above method is a mixture of (1) a polyol component decomposed to a low molecular weight, and (2) a large amount of polyhydric alcohol used in the decomposition, and this mixture is used in a post-process. Only after addition of propylene oxide becomes a polyol as a reaction component in the production of a polyurethane foam. Moreover,
In the above method, a large amount of polyhydric alcohol is added with propylene oxide, so that the proportion of components derived from polyurethane foam waste in the finally obtained regenerated polyol is limited. Other conventional attempts belonging to the Chemical Recycling Law include hydrolysis, ammonia decomposition, amine decomposition, alcohol decomposition, and transesterification, using alkali metal hydroxides, ammonia, amine polyhydric alcohols, etc. alone or in combination as chemical agents. And the like. However, in the above-mentioned chemical recycling method, (1) urethane foam is a reaction product of various polyisocyanate components, various polyol components, and the like, and further, in a situation where such various polyurethane foams are mixed. It is difficult to set decomposition conditions suitable for the purpose, and it takes a long time for the decomposition treatment (for example, 200 ° C., 15 hours). (2) As a result of the decomposition treatment, the target polyol component itself is decomposed to have a low molecular weight. Therefore, there are basic problems such as the inability to reproduce and recycle the polyol component, and the difficulty in separating and recovering the mixture due to the mixture of various decomposition products.

In the above-mentioned thermal recycling method, heat energy is recovered by burning a polyurethane foam. However, (1) the furnace material is heated due to a large amount of heat generated by the combustion, and (2) harmful chemical substances in the combustion are burned. There are problems such as the possibility of occurrence.

[0007]

As described above, the conventional polyurethane foam recycling method has not been put into practical use due to the problems of cost and the original purpose of recyclability. In particular, in the conventional chemical recycling method, the decomposition reaction does not stop at the urethane bond (s), which is a crosslinking point of the polyurethane foam, but also extends to the molecular chain of the polyol component, thereby lowering the molecular weight of the polyol component. It is pointed out that the recovery and recycling of the polyol component is impossible, and that the recovery and recycling of the low molecular weight decomposed product of the polyol component is difficult even if complicated pretreatment and post-treatment are performed.

[0008] It is an object of the present invention to selectively decompose the crosslinking points of polyurethane foam and to prepare a polyol component (polyol component such as polyether and polyester used as a reaction component in the production of polyurethane foam).
An object of the present invention is to provide a polyurethane foam recycling method in which a polyol component useful as a reaction component for the production of a polyurethane foam is recovered as a decomposition treatment product by suppressing cleavage and decomposition of a molecular chain of the polyurethane foam.

[0009]

The method of the present invention is a method for recycling a polyurethane foam in which an azole compound is added to a pulverized polyurethane foam and subjected to a thermal decomposition treatment to obtain a polyol component as a decomposition product.

That is, in the present invention, various problems are solved by using the above-mentioned azole compound as a decomposing agent, and the intended object is achieved.

The above-mentioned pulverized polyurethane foam preferably has a particle size of 5 to 15 mm.

The azole compound is preferably a triazole compound.

The polyurethane foam in the present invention is a polyurethane foam of various grades such as a flexible polyurethane foam, a semi-rigid polyurethane foam and a rigid polyurethane foam, and is a polyether polyurethane foam, a polyester polyurethane foam or a polyurethane foam obtained by combining these. Is included. The details will be supplementarily described later.

The azole compound in the present invention is an azole and other compounds having an azole structure in the molecule. Similarly, a triazole compound is a compound in which the azole structure has a triazole structure, that is, a triazole and a compound having a triazole structure in the molecule. And other compounds. The details will be supplementarily described later.

Typical polyurethane foams include a catalyst, a foaming agent, a foaming agent and, if necessary, a polyisocyanate component, a polyol component, and optionally a crosslinking agent. And foaming and curing in the presence of other additives. As blowing agents, lower halogenated hydrocarbons (fluorocarbons, chlorinated alkanes, etc.) have been frequently used, but the use of halogenated hydrocarbons has been restricted for the purpose of environmental protection. Tends to be frequently used. In the latter case, water is used as a reactive blowing agent (generation of CO ₂ gas) and a crosslinking agent (generation of amino group).

As the polyisocyanate component, 2
An isocyanate compound having one or three or more isocyanate groups or a mixture thereof is contained, and aromatic polyisocyanates and alicyclic polyisocyanates are frequently used industrially. And the like.

The polyol component includes a polyol composed of one or a mixture of two or more selected from a polyether polyol and a polyester polyol, which are frequently used in the reaction with a polyisocyanate component in the production of a polyurethane foam. Representative examples of the polyether polyol include a polyether polyol obtained by reacting a compound having two or more active hydrogen atoms or a mixture thereof with a lower alkylene oxide, and a polyether polyol and a polymerizable monomer. (Acrylonitrile, styrene, and the like), and examples thereof include modified products of polypropylene glycol (PPG) and PPG-acrylstyrene monomer graft polymer (POP). Examples of the polyester polyol include a linear polyol obtained as a derivative of (1) an aliphatic divalent carboxylic acid or another polycarboxylic acid and (2) a dihydric alcohol or another polyhydric alcohol. Includes polyester polyols, branched polyester polyols and mixtures thereof.

In the present invention, the particle size of the pulverized polyurethane foam is preferably 5 to 15 mm.
If it is smaller than 5 mm, the polyurethane foam will agglomerate due to heat generated during pulverization, making pulverization difficult. Also, 1
If it exceeds 5 mm, the supply of the polyurethane foam to the kneader or the extruder cannot be performed smoothly. Since the decomposition reactivity of the polyurethane foam is not affected by the size of the particle size, the upper limit of the particle size may be arbitrarily changed by changing the material supply port of the kneader extruder.

The above-mentioned azole compound as a decomposing agent in the present invention is a compound having a heterocyclic five-membered ring structure containing at least one nitrogen atom in the molecule, such as azole (unsubstituted azole), substituted azole, Other azole derivatives are included. Examples of the five-membered heterocyclic ring structure containing one or more nitrogen atoms include a thiazole ring, an imidazole ring, an imidazoline ring, and a triazole ring. Specific azole compounds include, for example, (1) imidazole, ( 2) 2-phenylimidazole (3) 2-methylimidazole (4) 2-mercaptoimidazoline,
(5) 3-amino-1,2,4-triazole, (6)
N-cyclohexyl-2-benzothiazole sulfenamide, (7) benzotriazole, and the like. Note that (1) is an unsubstituted azole, (2) to (5) are substituted azoles, and (6) and (7) are bicyclic azole derivatives. Further, in Example 1-6 described later, a triazole compound as a decomposing agent, that is, a compound containing a heterocyclic five-membered ring structure containing three nitrogen atoms in the molecule,
An embodiment using (5) 3-amino-1,2,4-triazole and (7) benzotriazole is shown.

The use ratio of the above decomposing agent is 0.1-1.0.
% By weight.

For the thermal decomposition treatment in the present invention, various reaction means having a heating means and a stirring and mixing means can be used, for example, a reaction tank with a heating furnace, an autoclave reaction tank (all with stirring and mixing means), A heating kneader type reaction tank, an extruder type reactor (with heating means) and the like can be mentioned.

In the present invention, the temperature for the thermal decomposition treatment is generally preferably from 180 ° C. to 200 ° C. (However, when an extruder type reactor or an extruder is used as a reaction means,
170 ° C-200 ° C because lower temperature decomposition is possible
It may be. Similarly, the time required for the thermal decomposition treatment is generally 5-20.
You can reach your goal in minutes. (However, when an extruder-type reactor or an extruder is used as a reaction means, a shorter time: 2-
It may be about 5 minutes. If the thermal decomposition treatment temperature exceeds 200 ° C., the carbonization reaction proceeds, which is not preferable because the polyurethane foam is carbonized. On the other hand, when the temperature of the heat decomposition treatment is set to 180 ° C. or lower, the decomposition reaction rate is undesirably low.

The mixture obtained after the thermal decomposition treatment obtained by the present invention can be added to and mixed with a polyol component in the production of a polyurethane foam to form a polyurethane foam, whereby the polyol component contained in the polyurethane foam waste can be renewed. A cycle in which the polyurethane foam is recycled and used as a constituent component is completed. In this case, it was determined that the by-product polyamines in the mixture after the completion of the thermal decomposition treatment did not need to be separated because there was no problem in the mechanical properties of the polyurethane foam produced by adding the regenerated polyol.

According to the present invention, the cleavage of the ether bond or the ester bond of the polyol, which is the object of recovery and utilization, is suppressed, and the urethane bond, which is a crosslinking point of the polyurethane foam, is selectively decomposed. A useful polyol as a polyol component can be recovered and used as a main effect component of the mixture after the heat decomposition treatment. Such selective promotion of urethane bond degradation is provided by the decomposing agent of the present invention. The mechanism of action is as follows.

Since the decomposing agent used in the present invention has an azole-type nitrogen-containing five-membered ring structure, it has a property as a π-excess system on one side and a π-deficient system on the other side due to a pyridine-type nitrogen atom. It has the property of On the other hand,
The heat dissociation of the urethane bond forming the cross-linking point of the polyurethane foam and the further replacement of the isocyanate group supposed to be generated as a result of the heat dissociation are promoted by the electron withdrawing reagent and the nucleophilic reagent, respectively. It is presumed that the two-sided nature of the electron withdrawing and nucleophilicity possessed by the azole compound is well balanced to promote the selective decomposition of urethane bonds. Alternatively, the required electron-withdrawing property or electron-donating property of the decomposing agent varies depending on the type of the polyisocyanate component and the polyol component used in the production of the polyurethane foam. It is presumed that the surface property has a binding promoting effect of urethane bond decomposition in the presence of various structures around the cross-linking point.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method embodying the present invention comprises, as essential reaction components, (1) a polyisocyanate component,
(2) The polyurethane foam waste product obtained by reacting with the polyol component has a proper size, e.g.
The crushed polyurethane foam is pulverized to a size of −15 mm, and the pulverized polyurethane foam is an azole compound, that is, a compound containing a heterocyclic five-membered ring structure containing one or more nitrogen atoms in the molecule (eg, azole, substituted azole compound, bicyclic azole compound Or a heat-decomposition treatment in the presence of a substituted derivative thereof or another azole derivative) to obtain a heat-decomposition-completed mixture containing a polyol component as a main effect component, which is useful as a polyol component in polyurethane foam production. Is the way. In the following examples, further embodied preferred embodiments are shown.

[0027]

Example 1 A pulverized polyurethane foam (particle size: 5 to 15 mm) was thermally decomposed in the presence of a decomposing agent under the following conditions to obtain a polyol for recycling. The apparatus uses a reaction apparatus having a heater, a stirring means, and a temperature measurement means for the reaction mixture.After the temperature of the reaction mixture reaches a predetermined temperature, the decomposition reaction is advanced while maintaining the predetermined temperature for a predetermined time, and the decomposition reaction is performed. Finished.

(1) Polyurethane foam: cut with a soft urethane foam contour machine for vehicle seat cushions and then pulverized with a pulverizer), particle size 15 mm (2) Decomposing agent: benzotriazole, 0.5% by weight (3) Reaction Temperature: 200 ° C. (4) Processing time: 20 minutes (Example 2) Under the following conditions, a thermal decomposition treatment was performed according to Example 1 to obtain a polyol for recycling.

(1) Polyurethane foam: soft urethane foam for vehicle seat cushion, particle size 15 mm (2) Decomposing agent: 3-amino-1,2,4 triazole,
0.5% by weight (3) Reaction temperature: 200 ° C. (4) Processing time: 20 minutes (Example 3) Under the following operating conditions, a thermal decomposition treatment was performed in accordance with Example 1, and A polyol was obtained.

(1) Polyurethane foam: rigid polyurethane foam for vehicle heat insulating material, particle size 15 mm (2) Decomposing agent: benzotriazole, 0.5% by weight (3) Reaction temperature: 200 ° C. (4) Processing time: 20 minutes (Example 4) Under the following conditions, a thermal decomposition treatment was carried out according to Example 1 to obtain a polyol for recycling.

(1) Polyurethane foam: rigid polyurethane foam for vehicle heat insulating material, particle size 15 mm (2) Decomposing agent: 3-amino-1,2,4 triazole,
0.5% by weight (3) Reaction temperature: 200 ° C. (4) Processing time: 20 minutes (Example 5) Under the following operating conditions, a thermal decomposition treatment was carried out in accordance with Example 1, and A polyol was obtained.

(1) Polyurethane foam: semi-rigid polyurethane foam for vehicle headrest, particle size 15 mm (2) Decomposing agent: benzotriazole, 0.5% by weight (3) Reaction temperature: 200 ° C. (4) Processing time: 20 minutes (Example 6) Under the following conditions, a thermal decomposition treatment was carried out according to Example 1 to obtain a polyol for recycling.

(1) Polyurethane foam: rigid polyurethane foam for vehicle heat insulating material, particle size 15 mm (2) Decomposing agent: 3-amino-1,2,4 triazole,
0.5% by weight (3) Reaction temperature: 200 ° C. (4) Processing time: 20 minutes In the above Examples 1 to 6, a flexible polyurethane foam (Examples 1 and 2) and a semi-rigid polyurethane foam (Example 5) And rigid polyurethane foam (Example 3,
The polyol component for recycling was recovered from 4,6). Reaction temperature as above: 200 ° C., treatment time: 20
Under the conditions of a decomposing agent of 0.5% by weight for one minute, a polyol component for recycling mainly comprising a polyol corresponding to each of the raw material polyol components of the flexible foam, the semi-rigid foam and the rigid foam was obtained. Such achievements include (1) promotion of selective decomposition of urethane bonds, (2) suppression of cleavage of ether bonds and ester bonds, (3) suppression of generation and mixing of decomposition products of polyol, and (4) short time. This is due to the termination of decomposition.

[0034]

As described above, the polyurethane foam waste is thermally decomposed in a short time without the need for complicated pre-treatment and post-treatment steps, thereby completing the thermal decomposition treatment useful as a polyol component in the production of polyurethane foam. A mixture can be obtained. This enables a recycling method for recycling polyurethane foam waste into polyurethane foam.

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[Procedure amendment]

[Submission date] May 27, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0025

[Correction method] Change

[Correction contents]

Since the decomposing agent used in the present invention has an azole-type nitrogen-containing five-membered ring structure, it has a property as a π-excess system on one side and a π-deficient system on the other side due to a pyridine-type nitrogen atom. It has the property of On the other hand,
The heat dissociation of the urethane bond forming the cross-linking point of the polyurethane foam and the further replacement of the isocyanate group supposed to be generated as a result of the heat dissociation are promoted by the electron withdrawing reagent and the nucleophilic reagent, respectively. It is presumed that the two-sided nature of the electron withdrawing and nucleophilicity possessed by the azole compound is well balanced to promote the selective decomposition of urethane bonds. In particular, triazole compounds have
The imino group acts as a nucleophile and isocyanate
Group substitution is promoted and ultimately urethane bond decomposition is promoted.
Is advanced. Alternatively, the required electron-withdrawing property or electron-donating property of the decomposing agent varies depending on the type of the polyisocyanate component and the polyol component used in the production of the polyurethane foam. It is presumed that the surface property has a binding promoting effect of urethane bond decomposition in the presence of various structures around the cross-linking point.

Claims (3)

[Claims] 1. A method for recycling a polyurethane foam in which an azole compound is added to a pulverized polyurethane foam and subjected to a thermal decomposition treatment to obtain a polyol component as a decomposition product. 2. The polyurethane foam recycling method according to claim 1, wherein the pulverized polyurethane foam is a polyurethane foam having a particle size of 5 to 15 mm. 3. The method according to claim 1, wherein the azole compound is a triazole compound.